Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CONTINUOUS-FLOW ELECTROMAGNETIC-INDUCTION FLUID HEATER
IN A VENDING MACHINE FOR PREPARING BEVERAGES
Cross-Reference To Related Patent Applications
This patent application claims priority from Italian patent application no.
102019000009384 filed on 18.06.2019, the entire disclosure of which is
incorporated
herein by reference.
Technical Field
The present invention relates in general to the field of vending machines for
preparing beverages, and in particular to a continuous-flow electromagnetic-
induction
fluid heater for heating a fluid, in particular water, milk, air or the like,
in a vending
machine for preparing beverages, in order to prepare hot beverages from an
anhydrous
material, for instance coffee, tea, hot chocolate or the like.
Background Art
Vending machines for preparing beverages, in particular hot beverages, from an
anhydrous material, for instance coffee, tea, hot chocolate or the like, are
known.
Such vending machines are provided with one or more heaters configured to heat
the water, for instance boilers or kettles. Known heaters generally comprise a
heating
element made of a resistive material and apt to heat the water held inside a
tank or
container of the machine.
More specifically, the heating element is permanently immersed in the water
held
in the container; a potential difference is applied to the ends of the heating
element. An
electric current is thus generated within the latter which, by the Joule
effect, dissipates
energy in the form of heat, thus heating the water by conduction.
It is thus necessary to maintain the water held in the container at a desired
temperature so as to guarantee a rapid dispensing of the beverage.
It follows that, if the machine remains inactive for long periods, a
considerable
amount of energy will be consumed to maintain the water inside the container
at the
desired temperature (usually above 85 C).
Moreover, the heaters mentioned above are of the accumulator type, i.e. of the
type
in which a given volume of water is held in the container and in which the
water is heated
and maintained at the desired temperature; when the dispensation of a certain
volume of
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hot water is requested to prepare a corresponding beverage, the hot water
drawn from the
container is replenished with water at room temperature. The water in the
container thus
needs to be heated and raised again to the desired temperature so as to
guarantee that the
next dispensation occurs at the desired temperature.
In the latter case, a waiting period is thus necessary for re-heating the
water, the
duration of which depends on the quantity of hot water dispensed during one or
more
previous dispensations.
Besides temperature, an important specification to be met is the flow rate of
the hot
water dispensed, which depends above all on the type of beverage to be
prepared; for
instance, in the case of beverages produced by means of soluble substances, a
considerable (at least 10 cc/s) flow rate of hot water is required. With a
high flow rate of
dispensed hot water, there will be a rapid drop in the temperature of the
water held in the
container, resulting in long waiting times for a subsequent dispensation or in
an obtained
beverage in which the soluble substance can form lumps.
FR-A-2855359, EP-A-1380243 and DE-A-102007034370 illustrate examples of
continuous-flow water heaters for heating water by means of heat produced with
electrical
resistances.
The problems described above relating to the heating of the water in vending
machines for preparing beverages stem from the thermal inertia with which a
given mass
of water heats up.
In order to remedy these technical drawbacks, solutions which exploit the
phenomenon of electromagnetic induction for heating the water are known.
In particular, continuous-flow water heaters are known which exploit
electromagnetic induction in order to generate parasitic currents within a
duct made of an
electrically conductive material inside which the water to be heated flows.
The parasitic
currents dissipate energy, by the Joule effect, in the form of heat, thus
heating the duct
and, consequently, the water that flows in contact with the same.
Electromagnetic induction heaters are known to be particularly advantageous
inasmuch as they allow a rapid heating of the water.
EP-A-2868242, of the present Applicant, describes a heater comprising a metal
duct
wound in the shape of a spiral and housed in a cavity of a spool made of an
electrically
insulating material and on which a winding of electromagnetic induction is
wound.
The winding is supplied with alternating electric current which generates, by
electromagnetic induction, parasitic currents which heat, by the Joule effect,
the spiral
metal duct and thus the water which flows inside the same.
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The spool is attached to the support structure of the machine, while the metal
duct
has no mechanical attachments with the spool, being simply supported by the
hydraulic
circuit to which it is connected by means of simple quick (push-in) fittings.
More specifically, the metal duct and the spool are separated radially by a
free space
(air gap).
This way, the maintenance of the heater and, in particular, the replacement of
the
metal duct is easier, more economical and simplified.
JP-A-2001284034 describes an example continuous-flow water heater by
electromagnetic induction.
Object and Summary of the Invention
Although the heater of the type described above represents a functionally
viable
solution for heating the water in vending machines for preparing beverages
from an
anhydrous material, the Applicant has had the opportunity to verify that the
known heaters
are capable of further improvement, in particular with respect to the
efficiency of the heat
exchange achievable by means of the heater.
The object of the present invention is to realize a continuous-flow
electromagnetic-
induction fluid heater, which is very reliable and of limited cost, and which
makes it
possible to satisfy the requirement specified above in connection with the
known heaters.
According to the invention, this object is achieved by a continuous-flow
electromagnetic-induction fluid heater and by a vending machine for preparing
hot
beverages comprising such a continuous-flow electromagnetic-induction fluid
heater as
claimed in the attached claims.
Brief Description of the Drawings
Figure 1 is a schematic perspective view, with parts removed for clarity, of a
supply
and heating assembly comprising a heater realized in accordance with a first
preferred
embodiment of the present invention;
Figure 2 illustrates, on an enlarged scale and with parts removed for clarity,
an axial
section along the line II-II shown in Figure 1;
Figure 3 illustrates a cross-section along the line III-III shown in Figure 2;
Figure 4 is analogous to Figure 2 and illustrates a corresponding axial
section, on
an enlarged scale and with parts removed for clarity, of a heater in
accordance with a
second preferred embodiment of the invention;
Figure 5 is analogous to Figure 3 and illustrates a corresponding cross-
section of
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the heater shown in Figure 4;
Figure 6 is analogous to Figure 2 and illustrates a corresponding axial
section, on
an enlarged scale and with parts removed for clarity, of a heater in
accordance with a third
preferred embodiment of the invention; and
Figure 7 is analogous to Figure 3 and illustrates a corresponding cross-
section of
the heater shown in Figure 6.
Detailed Description of Preferred Embodiments of the Invention
The present invention will be described in the following with reference to
water
heating without relinquishing any generality as a result, as it can also be
used to heat other
types of fluids utilized in vending machines for preparing beverages, in
particular liquid
milk or air used for emulsifying the liquid milk or fluids other than water.
With reference to Figures 1 to 3, a continuous-flow electromagnetic-induction
fluid
heater for heating a fluid, in particular water, in a vending machine for
preparing
beverages (not shown) in particular hot beverages from an anhydrous material,
for
instance coffee, tea, hot chocolate or the like, is indicated as a whole by 1.
In particular, the heater 1 is part of a supply and heating assembly 2 of the
aforementioned machine, which comprises:
- a hydraulic supply circuit 3 (shown schematically in Figure 1) provided
with a
container 4 containing water, preferably water at room temperature, and
configured to
conduct a flow of water from the container 4 towards the heating device 1 by
means of a
tube 5; and
- an electric circuit 6 (shown schematically in Figure 1), the function of
which will
be clarified in the following.
In detail, the heater 1 is connected to the electric circuit 6 and fluidically
connected
to the hydraulic circuit 3.
As shown in Figure 2, the heater 1 comprises a tubular body 7 internally
defining a
flow channel 7a for the water. The tubular body 7 is thus hollow, has a
longitudinal axis
A and comprises an inlet opening 8 through which the water to be heated
conveyed by
the hydraulic circuit 3 is fed, in use, to the channel 7a, and an outlet
opening 10 through
which the heated water flows out, in use, from the channel 7a.
According to this preferred and non-limiting embodiment, the tubular body 7 is
substantially rectilinear, while the channel 7a is obtained coaxially to the
axis A and has
a substantially circular cross-section.
According to an alternative embodiment not shown, the tubular body 7 and/or
the
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channel 7a may have a non-rectilinear configuration, for instance including
one or more
curved sections; moreover, the channel 7a may have a non-circular cross-
section (for
instance elliptical, oval, square, rectangular, polygonal, etc.).
The tubular body 7 is attached to an internal support structure (not shown) of
the
5 .. machine, in a known manner not described in detail.
In particular, the heater 1 comprises an upper end portion 14 and a lower end
portion
15, arranged on axially opposite sides of the tubular body 7, fixed to the
tubular body 7
and apt to be coupled (in particular mounted) to the internal support
structure of the
machine.
More particularly, the upper end portion 14 and the lower end portion 15
define
respective axial closing elements of the tubular body 7.
In one embodiment, the upper end portion 14 and the lower end portion 15 are
coupled to the tubular body 7 in a removable manner, for instance by means of
a threaded
coupling.
As shown in Figures 1 and 2, the inlet opening 8 and the outlet opening 10 are
defined by respective protuberances extending axially from the upper end
portion 14 and
from the lower end portion 15, respectively.
In detail, the upper end portion 14 defines internally a passage 17 which
connects
the inlet opening 8 fluidically to the channel 7a, thus permitting the water
to pass through
the upper end portion 14 and flow into the channel 7a.
Similarly, the lower end portion 15 defines internally a passage 18 which
connects
the channel 7a fluidically to the outlet opening 10, thus permitting the water
to pass
through the lower end portion 15 and flow out of the tubular body 7.
In light of the above, the inlet opening 8 and the outlet opening 10 are
arranged at
respective opposite axial ends of the tubular body 7.
In the example shown, the outlet opening 10 is fluidically connected to an
outlet
tube 16 (Figure 1). This outlet tube 16 is configured to conduct the heated
water from the
heating device 1 to a beverage production chamber (not shown), where the
heated water
laps the anhydrous material generally contained in a capsule pierced
beforehand. The thus
obtained beverage is then conveyed from the production chamber to a dispenser
(also not
shown), by means of which it is discharged from the machine.
The heater 1 further comprises a winding 11 defined by a plurality of
concentric
spirals 1 la wound directly in contact around an external surface 12 of the
tubular body 7.
In detail, the winding 11 is configured to be supplied with an alternating
electric
current at a given oscillation frequency and to generate, in this manner, an
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electromagnetic induction field.
In greater detail, the electric circuit 6 applies, in use, an alternating
voltage to
respective ends 1 lb of the winding 11, thus generating the aforementioned
alternating
electric current and the aforementioned electromagnetic induction field.
Preferably, the tubular body 7 is made of a material having zero magnetic
susceptibility.
In this way, the tubular body 7 interacts with the electromagnetic induction
field
generated by the winding 11 to a minimal extent or essentially not at all,
thus preventing
a disturbance of the latter.
The heater 1 further comprises a heating element 13, which is arranged inside
the
channel 7a so as to be lapped, in use, by the flow of water flowing inside
said channel 7a
and which can be activated, in use, by means of the electromagnetic induction
field
generated by the winding 11.
Specifically, by supplying the winding 11 with alternating electric current,
an
alternating electromagnetic induction field is generated, the flux lines of
which meet
inside the channel 7a and, in particular, pass through the heating element 13.
According
to Faraday's law, the variation in the resulting electromagnetic induction
field flux
generates parasitic currents inside the heating element 13, which heat the
heating element
13 by the Joule effect.
The heating element 13 is conveniently made of a ferromagnetic material. In
this
way, the lines of the electromagnetic induction field are closer together
inside the heating
element 13, optimizing the generation of the parasitic currents, and are not
dissipated
inside the tubular body 7.
In use, the water that flows inside the channel 7a laps the heating element 13
and is
therefore heated by means of a heat exchange by conduction.
As shown in Figure 2, the heating element 13 is radially spaced from the
tubular
body 7, more precisely from an internal surface 19 of the channel 7a, by means
of a gap
20 inside of which the water, in use, flows.
In detail, the heating element 13 extends axially inside the channel 7a, from
the
upper end portion 14 to the lower end portion 15 without ever contacting the
internal
surface 19 of the channel 7a. More specifically, the heating element 13 is
fixed to the
upper and lower end portions 14 and 15.
According to this preferred and non-limiting embodiment, the heating element
13
has a substantially circular cross-section and is housed inside the channel 7a
coaxially to
the axis A.
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Accordingly, the gap 20 has a substantially annular cross-section.
According to an alternative embodiment not shown, the heating element 13 may
have a non-circular cross-section, for instance elliptical, oval, square,
rectangular,
polygonal, etc.
In the example shown in Figures 2 and 3, the heating element 13 comprises, in
particular is constituted by, a single bar element.
As shown in Figures 1 and 2, the supply and heating assembly 2 further
comprises
a temperature sensor 21 configured to measure the temperature of the water at
the outlet
opening 10.
In particular, the sensor 21 is arranged, at least partially, inside the
passage 18 of
the lower end portion 15 of the heater 1 and is thus configured to measure,
with an
acceptable degree of approximation, the temperature of the water at the outlet
opening
10.
The assembly 2 further comprises a logic unit 22 configured to obtain the
temperature values measured by the sensor 21.
The logic unit 22 is also configured to control the activation and the
deactivation of
the electric circuit 6, as well as to control the oscillation frequency of the
alternating
voltage applied by the electric circuit 6 to the winding 11.
In use, based on the temperature value of the outgoing water measured by the
sensor
21, the logic unit 22 adjusts the oscillation frequency and thus the electric
power output
by the electric circuit 6. It is indeed known that a greater temperature
corresponds to a
greater electric power, as a result of the greater heat produced by the Joule
effect by the
heating element 13.
In this way, the logic unit 22 controls the variation of the temperature of
the
outgoing water.
Advantageously, the inlet opening 8 and the outlet opening 10 of the tubular
body
7 are arranged in respective eccentric positions with respect to the axis A.
In particular, the inlet opening 8 and the outlet opening 10 are arranged in
respective
diametrically opposite positions with respect to the axis A.
In this way, the water flows, in use, inside the channel 7a, from the inlet
opening 8
to the outlet opening 10, according to a non-laminar motion regime. Indeed, as
the two
inlet and outlet openings 8 and 10 are situated on diametrically opposite
sides with respect
to the axis A, the water flows inside the gap 20 in a vortex motion around the
heating
element 13 in such a manner as to render the contact of the fluid with said
heating element
13 uniform.
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The operation of the heater 1 according to the present invention will be
described
in the following, with particular reference to an initial condition in which
the water at
room temperature is inside the container 4.
In this condition, when a user orders the dispensing of a beverage, the logic
unit 22
allows, by means of a system of valves and pumps of a known type (shown
schematically
in Figure 1), the flow of water to be heated through the inlet opening 8 and
the passage
17 inside the tubular body 7.
Simultaneously, the logic unit 22 controls the activation of the electric
circuit 6,
which applies an alternating voltage at a given frequency to the ends 1 lb of
the winding
11, thus generating an alternating electric current, which in turn generates
the
aforementioned electromagnetic induction field.
As described above, this field causes the heating of the heating element 13,
which
heats the water flowing inside the channel 7a and lapping said heating element
13.
When the heated water flows through the passage 18, the sensor 21 measures its
temperature and sends the measured value to the logic unit 21. This way, a
closed-loop
control of the measured temperature is achieved.
The heated water is then conveyed by means of the tube 16 to the chamber for
producing the selected beverage.
With reference to Figures 4 and 5, a continuous-flow heater realized in
accordance
with an alternative preferred embodiment of the present invention is indicated
as a whole
by 1'.
Since the heater 1' is similar by structure and operation to the heater 1,
only the
structural and functional differences with respect to the latter will be
described in the
following.
The same references will be used to indicate similar or equivalent parts
and/or
features.
In particular, the heater 1' differs from the heater 1 in that it is provided
with a
heating element 13' which comprises, in particular is constituted by, a
plurality of bar
elements.
More specifically, the heating element 13' is constituted by a bundle of bar
elements
having a smaller diameter than the diameter of the single bar element forming
the heating
element 13 of the heater 1.
Specifically, each of the bar elements of the heating element 13' extends
axially
inside the channel 7a, from the upper end portion 14 to the lower end portion
15.
More specifically, the bar elements are fixed to these upper and lower ends
portions
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14 and 15.
In use, the flow of water flowing inside the channel 7a laps each of the bar
elements,
running in the interstices of the channel 7a between the bar elements. The
heat exchange
is improved as a result, as the total transfer surface of the heating element
13' is greater
than that of the heating element 13.
With reference to Figures 6 and 7, a continuous-flow heater realized in
accordance
with a further preferred embodiment of the present invention is indicated as a
whole by
1".
Since the heater 1" is similar by structure and operation to the heater 1,
only the
structural and functional differences with respect to the latter will be
described in the
following.
The same references will be used to indicate similar or equivalent parts
and/or
features.
In particular, the heater 1" differs from the heater 1 in that it is provided
with a
heating element 13" which comprises, in particular is constituted by, a
plurality of thin
wall sheets.
Specifically, each of the sheets of the heating element 13" extends axially
inside
the channel 7a, from the upper end portion 14 to the lower end portion 15.
More specifically, the sheets are fixed to these upper and lower ends portions
14
and 15.
In use, the flow of water flowing inside the channel 7a laps each of the thin
wall
sheets, running in the interstices delimited between each pair of sheets. The
heat exchange
is improved as a result, as the total exchange surface of the heating element
13" is even
greater than that of the heating element 13'.
From an examination of the features of the heaters 1, l', 1" realized in
accordance
with the present invention, the advantages rendered achievable by the same
become
evident.
In particular, as a result of the arrangement of the inlet and outlet openings
8 and
10, it is possible to achieve a uniform flow of the water inside the channel
7a of the tubular
body 7 so as to achieve a substantially vortex flow around the heating element
13, 13',
13" and thus an efficient and more uniform heat exchange with the latter.
Moreover, as a result of the shape of the heating element 13', it is possible
to
achieve an improved heat exchange, since the exchange surface is greater than
that of the
heating element 13.
Furthermore, as a result of the shape of the heating element 13", this
improvement
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is even more perceptible, since the ratio between the exchange surface and the
volume of
the heating element 13" is greater in relation to the ratio between the
exchange surface
and the volume of the heating element 13, 13'.
It is evident that the described and shown heaters 1, 1', 1" can be modified
and
5 varied without leaving the scope of protection defined by the claims as a
result.
